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Fig. 4. Comparison of insulin and glucagon expression in the pre- and post-metamorphic pancreases. (A,D,E,F) Insulin expression (B,C) Glucagon expression. At late stages, insulin is expressed throughout the whole pancreas in much larger groups of cells in the dorsal pancreas than in the ventral pancreas. (B) Insulin in red and glucagon in blue. Glucagon and insulin-expressing cells form discrete groups of cells that do not overlap. No islets are seen with glucagon cells surrounding insulin cells. (C) Section through a stage 47 pancreas showing glucagon expression in small groups on the periphery of the pancreas. (D–F) Serial sections through a late pancreas, around stage 47. Every other section is shown and therefore each section is 15 μm apart. Note the discrete groups of insulin cells on the periphery and the lighter internal staining cells (arrowhead). Also note the hollow center in the insulin groups (F, arrow). (G–I) Double in situ hybridization for insulin (magenta) and glucagon (blue). (G) Stage 54 tadpole pancreas. (H,I) Froglet pancreas. As seen in earlier stages, glucagon-expressing cells do not surround the insulin-expressing cells (arrows). Glucagon-expressing cells are found exclusively at the periphery of the pancreas, while insulin-expressing cells form large interconnected groups throughout the whole pancreas. H and I are sections from the same froglet pancreas 42 μm apart. |
